Revenue Recognition Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 03, 2021	Apr. 04, 2020	Apr. 03, 2021	Apr. 04, 2020
Disaggregation of Revenue [Line Items]
Net sales	$ 373,982	$ 293,147	$ 700,035	$ 613,918
OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	223,248	173,722	434,410	374,670
Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	150,734	119,425	265,625	239,248
Products | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	130,458	101,860	256,035	211,696
Products | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	121,610	92,693	210,922	186,596
Other products and services revenues | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	92,790	71,862	178,375	162,974
Other products and services revenues | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	29,124	26,732	54,703	52,652
Sales of spare parts
Disaggregation of Revenue [Line Items]
Net sales	16,500	15,300	32,500	30,900
Microelectronics | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	138,181	104,901	266,354	219,794
Microelectronics | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	30,096	16,866	50,771	32,519
Precision manufacturing | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	15,771	8,397	27,630	18,792
Precision manufacturing | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	91,627	77,910	161,218	155,887
Instrumentation | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	67,078	56,838	134,354	125,024
Instrumentation | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	21,255	16,570	39,206	35,564
Aerospace and defense | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	2,218	3,586	6,072	11,060
Aerospace and defense | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	$ 7,756	$ 8,079	$ 14,430	$ 15,278